Method for producing zeolites

ABSTRACT

As synthesized by previous methods, ZSM-5 or ZSM-11 zeolites are crystallized in the presence of substantial amounts of a nitrogen-containing compound. When synthesized in this way, they contain an organic ammonium cation as well as a metal cation such as sodium. To obtain a more active form, the sodium ion must be exchanged out. Such exchange, especially with ZSM-5 and ZSM-11, is difficult unless there is calcination of the zeolite to remove the obstructing organo compounds. By making these zeolites in the presence of (1) seeds of the desired zeolite, (2) mixtures of them with ammonium hydroxide and/or alcohol, (3) the alcohol per se or (4) mixtures of the alcohol with ammonium hydroxide, a product substantially deficient in organic ammonium cation is obtained. These products can be exchanged directly without any calcination.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a Continuation-In-Part of United States application Ser. No.650,481, filed Jan. 19, 1976, which in turn is a Continuation-In-Part ofUnited States application Ser. No. 424,481, filed Dec. 13, 1973, bothabandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a process for making zeolites. Moreparticularly it relates to making ZSM-5 or ZSM-11 zeolites which, intheir synthesized form, are low in nitrogen content.

2. Summary of the Prior Art

Zeolites of the ZSM-5 type (e.g. ZSM-5 and ZSM-11) and others likezeolite Beta, TEA mordenite and ZSM-12 have been crystallized from asolution containing organic cations, particularly including alkylammonium cations. Zeolites ZSM-5 and ZSM-11, in general, have a poresize greater than the 5 Angstrom materials and less than the large porezeolites such as Zeolite X, Zeolite Beta and the like.

U.S. Pat. No. 3,702,886 is concerned with the zeolite ZSM-5 and some ofits uses. U.S. Pat. No. 3,709,979 discloses and claims ZSM-11. So thedescription of these two zeolites may be complete, the two U.S. patentsare hereby incorporated herein by reference. Neither of these patentssuggests or teaches the use of ZSM-5 or ZSM-11 seeds to prepare therespective zeolites.

In addition, U.S. Pat. No. 3,119,659 discloses the use of the same typeof molecular sieve being produced, as do U.S. Pat. No. 3,321,272 andU.S. Pat. No. 3,532,459. U.S. Pat. No. 3,671,191 teaches a generalseeding technique, as does an article by Zhdanov, "Molecular SieveZeolites-I" ACS, 1971, pages 36 and 37. German No. 2,212,810 disclosesthe use of a mixture of ethyl alcohol, ammonium hydroxide andtriethylamine to make ZSM-8 and of a mixture of ammonia, propyl alcoholand tripropylamine to make ZSM-5.

SUMMARY OF THE INVENTION

In accordance with the invention, there is provided a method forsynthesizing a ZSM-5 or ZSM-11 crystalline aluminosilicate substantiallydeficient in nitrogen, preferably no more than about 0.2% by weight,which comprises carrying out the reaction to form said zeolite in thepresence of a member selected from the group consisting of ZSM-5 seeds,ZSM-11 seeds and mixtures thereof with NH₄ OH and/or alcohol. It is tobe understood that when seeds are used, ZSM-5 seeds produce ZSM-5 andZSM-11 seeds produce ZSM-11. This is true whether they are used alone orin a mixture as set forth. It will also be understood that the membersincluded are: (1) ZSM-5 or ZSM-11 seeds; (2) ZSM-5 or ZSM-11 seeds plusalcohol; (3) ZSM-5 or ZSM-11 seeds plus NH₄ OH; (4) ZSM-5 or ZSM-11seeds plus alcohol plus NH₄ OH; (5) alcohol; and (6) alcohol plus NH₄OH.

The aliphatic alcohol preferably is an alcohol containing 2 to 5 carbonatoms. Illustrative are ethanol, propanol, butanol and pentanol. It iscontemplated that the alcohols may be straight or branch chain.

ZSM-5 and ZSM-11 seeds may be from previously prepared batches of ZSM-5or ZSM-11 made by present methods. Alternatively, seeds of ZSM-5 orZSM-11 prepared by the process of this invention may be used.Furthermore, it has been discovered that when subsequent batches ofZSM-5 or ZSM-11 zeolites are made in the same equipment, the residualzeolite is sufficient to supply the requisite amount of seeds.

Only a small amount of seeds are needed for the practice of thisinvention. Generally, from about 0.01% by weight to about 10% by weightof final product is sufficient. We prefer, however, to use from about 1%by weight to 6% by weight.

DESCRIPTION OF SPECIFIC EMBODIMENTS

ZSM-5 has the characteristic X-ray diffraction pattern set forth inTable 1 of U.S. Pat. No. 3,702,866, whether produced by prior artmethods or by the method of this invention. ZSM-5 compositions (as wellas ZSM-11 compositions) can also be identified in terms of mole ratiosof oxides as follows:

    0.9±0.2M.sub.2/n O:W.sub.2 O.sub.3 :XYO.sub.2 :ZH.sub.2 O

wherein M is a cation, n is the valence of said cation, W is selectedfrom the group consisting of aluminum and gallium, Y is selected fromthe group consisting of silicon and germanium, X is from about 5 toabout 3000 and Z is from 0 to 40. In a preferred form as synthesized byprior art methods the zeolite has a formula, in terms of mole ratios ofoxides as follows:

    0.9±0.2M.sub.2/n O:Al.sub.2 O.sub.3 :XSiO.sub.2 :ZH.sub.2 O

wherein M is selected from the group consisting of a mixture of alkalimetal cations, especially sodium, and tetraalklammonium cations, thealkyl groups of which preferably contain 2-5 carbon atoms. In thispreferred embodiment of ZSM-5, W is aluminum and Y is silicon. Also thepreferred silica/alumina ratio is from about 15 to about 900. Morepreferably, the silica/alumina ratio is from about 30 to about 350.

Zeolite ZSM-5 is prepared by prior art methods by preparing a solutioncontaining water, tetrapropyl ammonium hydroxide and the elements ofsodium oxide, an oxide of aluminum or gallium and an oxide of silica,and having a composition, in terms of mole ratios of oxides, fallingwithin the following ranges:

                  Table A                                                         ______________________________________                                                                     Particularly                                              Broad    Preferred  Preferred                                        ______________________________________                                         ##STR1##   0.07-1.0   0.1-0.8     0.2-0.75                                    ##STR2##    0.2-0.95  0.3-0.9    0.4-0.9                                      ##STR3##    10-300     10-300     10-300                                      ##STR4##    5-100     10-60      10-40                                       ______________________________________                                    

The solution is maintained at reaction conditions until the crystals ofthe zeolite are formed. Thereafter the crystals are separated from theliquid and recovered. Typical reaction conditions consist of atemperature of from about 75° C. to 175° C. for a period of about sixhours to 60 days. A more preferred temperature range is from about 90°to 150° C., with the amount of time at a temperature in such range beingfrom about 12 hours to 20 days.

For complete details of the preparation of ZSM-5 by a prior art method,U.S. Pat. No. 3,702,886 is incorporated herein by reference.

ZSM-11 can be suitably prepared by prior art methods, by preparing asolution (R₄ X)₂ O, sodium oxide, an oxide of aluminum or gallium, anoxide of silicon or germanium and water and having a composition, interms of mole ratios of oxides, falling within the following ranges:

                  Table B                                                         ______________________________________                                                   Broad    Preferred                                                 ______________________________________                                         ##STR5##      10-150    20-90                                                 ##STR6##     0.05-0.70  0.05-0.40                                             ##STR7##     0.02-0.20  0.02-0.15                                             ##STR8##      50-800    100-600                                              ______________________________________                                    

wherein R₄ X is a cation of a quarternary compound of an element ofGroup 5A of the Periodic Table, W is aluminum or gallium and Y issilicon or germanium maintaining the mixture until crystals of thezeolite are formed. Preferably, crystallization is performed underpressure in an stirred autoclave or static bomb reactor. The temperatureranges from 100° C. to 200° C. generally, but at lower temperatures,e.g. about 100° C., crystallization time is longer. Thereafter thecrystals are separated from the liquid and recovered. The new zeolite ispreferably formed in an aluminosilicate form.

For complete details of the preparation of ZSM-11, U.S. Pat. No.3,709,979 is incorporated herein by reference.

In preferred form, the zeolite made by the method of this invention, hasa formula, in terms of mole ratios of oxides, as follows:

    0.9±0.3M.sub.2/n O:Al.sub.2 O.sub.3 :30-350SiO.sub.2 :ZH.sub.2 O

wherein M is an alkali metal or an alkaline earth metal and Z is 0 to40.

The ZSM-5 made by the method of this invention is, as is the samezeolite made according to the prior art, preferably formed as thealuminosilicate, and it can be prepared utilizing materials which supplythe elements of the appropriate oxide. Such materials include aluminumsulfate, a mineral acid such as sulfuric acid, sodium aluminate,alumina, sodium silicate, silica hydrosol, silica gel, silicic acid,sodium hydroxide, along with the reagents of the improved method of thisinvention. It will be understood that each oxide component utilized inthe reaction mixture for preparing ZSM-5 can be supplied by one or moreinitial reactants, and they can be mixed together in any order. Forexample, sodium oxide can be supplied by an aqueous solution of sodiumhydroxide or an aqueous solution of sodium silicate. To make the ZSM-5using the present invention, a solution similar to that mentioned forTable A, but having a composition comprising materials having thefollowing mole ratios of oxides may be used:

                  Table C                                                         ______________________________________                                                                     Particularly                                             Broad     Preferred  Preferred                                        ______________________________________                                         ##STR9##  0.07-1.0    0.1-0.8     0.2-0.75                                    ##STR10##                                                                                10-300      10-300     10-300                                      ##STR11##                                                                                5-100      10-60      10-40                                        ##STR12##                                                                                0-400       0-300      0-150                                       ##STR13##                                                                                0-250       0-150      0-100                                      ______________________________________                                    

It should be noted that in Table C the OH⁻ in the NH₄ OH is not includedin the two ratios including that ion.

The reaction mixture can be prepared in either a batchwise or continuousmanner. Crystal size and crystallization time of the ZSM-5 compositionwill vary with the nature of the reaction mixture employed.

ZSM-11 made by the method of this invention is also preferably made asthe aluminosilicate utilizing reactants which supply the needed oxides.Thus, the reaction mixture may comprise reactants to yield an alkalimetal oxide, e.g. sodium oxide, alumina and silica. The reactionmixture, which also comprises water and the reagents of the presentimproved method, will have a composition, in terms of mole ratios ofoxides, as follows:

                  Table D                                                         ______________________________________                                                   Broad    Preferred                                                 ______________________________________                                         ##STR14##     10-150    20-90                                                 ##STR15##    0.05-0.70  0.05-0.40                                             ##STR16##     50-800    100-600                                               ##STR17##     0-400      0-300                                                ##STR18##     0-250      0-150                                               ______________________________________                                    

The ZSM-5 and ZSM-11 zeolites produced by the method of the presentinvention have, as has already been stated, essentially the same x-raydiffraction as those prepared by conventional prior art methods. Theproducts can also be expressed in terms of mole ratios of oxides as setforth hereinabove.

The ZSM-5 and ZSM-11 zeolites, as prepared by prior art methods, areuseful, for example, as cracking and hydrocracking catalysts as well ascatalysts for M-forming and dewaxing. However, in order to increasetheir range of activities and their stability, it is necessary to removethe original metal ion, usually sodium. The original metal of mostzeolites can be removed by conventional exchange procedures, as bymultiple exchanges, i.e. one exchange followed by another, etc. Somezeolites, ZSM-5 and ZSM-11 included, are not suspectible to this methodof exchange, the sodium content reaching a plateau and remaining thereregardless of the number of additional exchanges. It has been previouslydiscovered that calcination of the zeolite by removing the organicN-containing cations "frees" the sodium so it can thereafter be removedeasily. Typical replacing cations would include hydrogen, ammonium andmetal cations, including mixtures of the same. Of the replacing cations,particular preference is given to cations of hydrogen, ammonium, rareearth, magnesium, zinc, calcium, nickel, and mixtures thereof, generallyemployed in the form of their salts, preferably the chlorides, nitratesor sulfates. This precalcination is not necessary, although it may stillbe used to remove the sodium cation from the products of this invention.

Representative, more detailed ion exchange techniques are disclosed in awide variety of patents, including U.S. Pat. Nos. 3,140,249, 3,140,251,3,140,253 and 3,702,866.

Following contact with the salt solution of the desired replacingcation, the zeolites prepared in accordance with this invention may bewashed with water and dried at a temperature ranging from 150° F. toabout 600° F. and thereafter may be heated in air or other inert gas attemperatures ranging from about 500° F. to 1500° F. for periods of timeranging from 1 to 48 hours or more. The zeolites thus produced andtreated are also useful as cracking catalyst in cracking, hydrocracking,M-forming and dewaxing operation.

It is also possible to treat the zeolite with steam at elevatedtemperatures ranging from 800° F. to 1800° F. and preferably 1000° F.and 1500° F., if such is desired. The treatment may be accomplished inatmospheres consisting partially or entirely of steam.

A similar treatment can be accomplished at lower temperatures andelevated pressures, e.g. 350°-700° F. at 10 to about 200 atmospheres.

The zeolites produced in the method of this invention may be used in aporous matrix. The zeolites can be combined, dispersed or otherwiseintimately admixed with a porous matrix in such proportions that theresulting product contains from 1% to 95% by weight, and preferably from1 to 70% by weight of the zeolite in the final composite.

The term "porous matrix" includes inorganic compositions with which thealuminosilicates can be combined, dispersed or otherwise intimatelyadmixed wherein the matrix may be active or inactive. It is to beunderstood that the porosity of the compositions employed as a matrixcan either be inherent in the particular material or it can beintroduced by mechanical or chemical means. Inorganic compositionsespecially those of a siliceous nature are preferred. Of these matricesinorganic oxides such as clay, chemically treated clay, alumina, silica,silica-alumina, etc. are particularly preferred because of theirsuperior porosity, attrition resistance, and stability. More preferably,alumina is the matrix, and it is preferably combined with the zeoliteprior to calcination.

Techniques for incorporating the zeolites in a matrix are conventionalin the art and are set forth in U.S. Pat. No. 3,140,253.

The following Examples serve to illustrate the scope of the inventionshowing that ZSM-5 crystalline aluminosilicates containing very lowlevels of organic nitrogen can be made by various techniques. It will beunderstood that the examples are not intended in any way to place alimitation on the invention.

A typical preparation of ZSM-5 according to the invention is givenhereinbelow. The details and results for the product produced are listedin Example 1 of Table 1. An acid alumina solution comprising 12.3 gms ofAl₂ (SO₄)₃.18H₂ O, 30.0 gms 98% H₂ SO₄ and 600 gms of H₂ O was added toa sodium silicate solution made by mixing 360 gms of Q-Brand sodiumsilicate (28.8% SiO₂, 8.9% Na₂ O, 62.4% H₂ O) and 450 gms water. To theresultant gel was added 124 gms ethanol. The gel was mixed with thealcohol until homogeneous and crystallized at autogenous pressure in astirred autoclave at 350° F. for 24 hours. The resultant solid materialwas water washed and dried at 230° F.

Examples 2-12 were made in a similar manner using the ingredients andconditions as shown in Tables 1-5.

Several of these examples were ion exchanged with ammonium salts withoutany prior calcination to show that sodium was easily replaced in such aprocedure. Results were excellent as indicated in the appropriatetables.

                  Table 1                                                         ______________________________________                                                          Ethanol                                                     Example             1          2                                              ______________________________________                                        Mix Components, gms                                                            A. Q Brand         360        360                                              H.sub.2 O         450        450                                             B. Al.sub.2 (SO.sub.4).sub.3 . 18H.sub.2 O                                                       12.3       12.3                                             H.sub.2 SO.sub.4 (98%)                                                                          30.0       30.0                                             H.sub.2 O         600        600                                             C. Ethanol         124        124                                            Mole Ratio of Mix                                                             Ethanol             146        146                                            Na.sub.2 O          8.6        8.6                                            Al.sub.2 O.sub.3    1.0        1.0                                            SiO.sub.2           94         94                                             H.sub.2 O           3870       3870                                           Na.sub.2 SO.sub.4   19.0       19.0                                           Crystallization     Stirred    Stirred                                        Temp., °F.   350        350                                            Time, hrs            24         24                                            Product                                                                       X-Ray Analysis      ZSM-5      ZSM-5                                          % Crystallinity     90         135                                            Composition, wt %                                                             N                   0.03       <0.01                                          Na                  1.2        1.0                                            Al.sub.2 O.sub.3    2.35       2.07                                           SiO.sub.2           94.5       93.8                                           Composition, mole Ratio                                                       N.sub.2 O           0.05                                                      Na.sub.2 O          1.14       1.07                                           Al.sub.2 O.sub.3    1.0        1.0                                            SiO.sub.2           68.5       77.0                                           Catalytic Properties                                                          M-Forming Screening Test (600° F., 400 psig, 15 WHSV,                  3/1 H.sub.2 /HC) (1.5 g catalyst - charged 50/50 wt                           n-heptane/benzene)                                                            Type Catalyst       H.sup.+ (1)                                                                              H.sup.+                                        n-Heptane Conv. wt %                                                                              65.4       68.2                                           Benzene Conv., wt % 24.6       27.1                                           C.sub.7.sup.+  Aromatics Prod., wt %                                                              21.4       23.2                                           Selectivity         0.28       0.28                                           ______________________________________                                         .sup.(1) Precalcination, 1000° F. + NH.sub.4 Exchange             

                  Table 2                                                         ______________________________________                                                          Ethanol and Seeds                                           Example             3          4                                              ______________________________________                                        Starting Compositions, gms.                                                    A. Q-Brand         45.0       360                                              H.sub.2 O         56.3       450                                             B. Al.sub.2 (SO.sub.4).sub.3 . 18H.sub.2 O                                                       1.54       12.3                                             H.sub.2 SO.sub.4 (98%)                                                                          3.75       30.0                                             H.sub.2 O         77.0       600                                             C. Ethanol         15.5       94.0                                            D. ZSM-5 seeds     3.25       26.0                                             (19.3% Solids)                                                              Mix Ratio - Moles                                                             Ethanol             111.0      111.0                                          Na.sub.2 O          8.6        8.6                                            Na.sub.2 SO.sub.4   19.0       19.0                                           Al.sub.2 O.sub.3    1.0        1.0                                            SiO.sub.2           94.0       94.0                                           H.sub.2 O           3870       3870                                           Crystallization, Temp. °F.                                                                 350        350                                               Time, hrs        97         21                                             Product                                                                       X-Ray Analysis      ZSM-5      ZSM-5                                          % Crystallinity     90         80                                             Composition, wt %                                                             N                   0.024      0.037                                          Na                  1.50       1.20                                           Al.sub.2 O.sub.3    2.21       4.15                                           SiO.sub.2                      97.7                                           Composition, Molar Ratio                                                      Na.sub.2 O          1.5        0.64                                           Al.sub.2 O.sub.3    1.0        1.0                                            SiO.sub.2                      40.0                                           ______________________________________                                    

                  Table 3                                                         ______________________________________                                                           Seeds Only                                                 Examples             5         6                                              ______________________________________                                        Starting Components, gms.                                                      A. Q-Brand          45.0      450                                              H.sub.2 O          56.3      563                                             B. Al.sub.2 (SO.sub.4) . 18H.sub.2 O                                                              1.54      15.4                                             H.sub.2 SO.sub.4 (98%)                                                                           3.75      37.5                                             H.sub.2 O          77.0      770                                             C. ZSM-5 seeds                                                               (19.3% Solids)                                                                  32.5                                                                        Mixed Ratio - Moles                                                           Na.sub.2 O           8.6       8.6                                            Na.sub.2 SO.sub.4    19.0      19.0                                           Al.sub.2 O.sub.3     1.0       1.0                                            SiO.sub.2            94.0      94.0                                           H.sub.2 O            3870      3870                                           ZSM-5, % Final Product                                                                             5.7       5.7                                            Crystallization      Static    Stirred                                           Temp. °F.  350       350                                               Time, hrs.         96        24                                            Product                                                                       X-Ray Analysis       ZSM-5     ZSM-5                                          % Crystallinity      90        105                                            Composition, wt %                                                             N                    0.02      0.03                                           Na                   1.50(1)   1.79.sup.(1)                                   Al.sub.2 O.sub.3     2.40      2.44                                           SiO.sub.2                      97.2                                           Composition, Molar Ratio                                                      Na.sub.2 O           1.38      1.63                                           Al.sub.2 O.sub.3     1.0       1.0                                            SiO.sub.2                      67.8                                           Catalytic Properties                                                          (M-Forming Screening Test) (600° F., 400 psig,                         15 WHSV, 3/1 H.sub.2 /HC, 1.5 gms. cat.)                                      Type Catalyst              H.sup.+ (2)                                        n-Heptane Conv., wt %      89.6                                               Benzene, Conv., wt %       30.8                                               C.sub.7.sup.+ Aromatics Prod., wt %                                                                      29.2                                               Selectivity                0.31                                               ______________________________________                                         .sup.(1) This value is reduced to 0.087% on Example 5 and 0.04% on Exampl     6 when exchanged with NH.sub.4 Cl without any precalcination.                 .sup.(2) Precalcination, 1000° F. + NH.sub.4 exchange.            

                  Table 4                                                         ______________________________________                                                              Ethanol                                                                       + NH.sub.4 OH                                           Example                 7                                                     ______________________________________                                        Mix Components, gms                                                            A. Q Brand             362                                                     H.sub.2 O             478                                                    B. Al.sub.2 (SO.sub.4).sub.3 . 18H.sub.2 O                                                           13.1                                                    H.sub.2 SO.sub.4 (98%)                                                                              31.9                                                    H.sub.2 O             658                                                    C. Ethanol             131                                                     NH.sub.4 OH, Conc., ml                                                                              148                                                   Mole Ratio of Mix                                                             Ethanol                 146                                                   NH4OH                   114                                                   Na.sub.2 O              8.6                                                   Al.sub.2 O.sub.3        1.0                                                   SiO.sub.2               94.0                                                  H.sub.2 O               3870                                                  Na.sub.2 SO.sub.4       19.0                                                  Crystallization         Stirred                                               Temp., °F.       350                                                   Time, hrs                21                                                   Product                                                                       X-Ray Analysis          ZSM-5                                                 % Cryst.                110                                                   Composition, wt %                                                             N                       0.044                                                 Na                      0.94                                                  Al.sub.2 O.sub.3        2.41                                                  SiO.sub.2               96.1                                                  Composition, mole Ratio                                                       N.sub.2 O               0.07                                                  Na.sub.2 O              0.87                                                  Al.sub.2 O.sub.3        1.00                                                  SiO.sub.2               67.8                                                  Catalytic Properties                                                          M-Forming Screening Test (600° F., 400 psig,                           15 WHSV, 3/1 H.sub.2 /HC)                                                     (1.5 g catalyst-charged 50/50 wt n-heptane/benzene)                           Type Catalyst           H.sup.+  (1)                                          n-Heptane Conv., wt %   76.6                                                  Benzene Conv., wt %     26.4                                                  C.sub.7.sup.+ Aromatics Prod., wt %                                                                   24.9                                                  Selectivity             0.31                                                  ______________________________________                                         .sup.(1) Nh.sub.4 Exch., 210° F. without precalcination Na = 0.01%

                                      Table 5                                     __________________________________________________________________________                    Ethanol + NH.sub.4 OH + Seeds                                 Example         8    9    10   11   12                                        __________________________________________________________________________    Mix Components - gms                                                           A. Q-Brand     360  45   45   255.2                                                                              45                                          H.sub.2 O     450  56.3 56.3 280  56.3                                        Ludox (29.5% SiO.sub.2)                                                                     450  56.3 56.3 280  56.3                                       B. Al.sub.2 (SO.sub.4).sub.3 . 18H.sub.2 O                                                   12.42                                                                              1.54 1.54 20.0 6.0                                         H.sub.2 SO.sub.4                                                                            30.0 3.75 3.75 20.0 2.25                                        H.sub.2 O     616  77.0 77.0 480  77.0                                       C. Ethanol     124  15.5 15.5 124  15.5                                        NH.sub.4 OH conc., ml.                                                                      140  17.5 17.5 140  17.5                                       D. ZSM-5 seeds (19.3% solids)                                                                26.0 3.25 3.25 21.0 3.25                                      Mole Ratio of Mix                                                             Ethanol         73   73   146  90   336                                       NH.sub.4 OH     115  115  115  69   28.5                                      Na.sub.2 O      8.6  8.6  8.6  2.56 1.66                                      Al.sub.2 O.sub.3                                                                              1.0  1.0  1.0  1.0  1.0                                       SiO.sub.2       94.0 94.0 94.0 40.8 23.9                                      H.sub.2 O       3870 2870 3870 1700 990                                       Na.sub.2 SO.sub.4                                                                             19.0 19.0 19.0 9.7  5.4                                       ZSM-5 Seeds, % Final Product                                                                  5.7  5.7  5.7  5.5  4.5                                       Crystallization stirred                                                                            static                                                                             static                                                                             stirred                                                                            static                                    Temp., °F.                                                                             350  446  255  350  400                                       Time, hrs.       17   22  334  120  96                                        Product                                                                       X-Ray Analysis  ZSM-5                                                                              ZSM-5                                                                              ZSM-5                                                                              ZSM-5                                                                              ZSM-5                                     % Cryst.        95   110  95   80   65                                        Composition, wt %                                                                             0.053                                                                              0.13 0.19 0.011                                                                              0.016                                     N               0.42                                                          C               1.3.sup.(1)                                                                        0.98      1.7.sup.(1)                                                                        3.2                                       Na              2.53 2.13      4.36 6.40                                      Al.sub.2 O.sub.3                                                                              97.2 95.6      92.8 88.2                                      SiO.sub.2                                                                     Composition, mole ratio                                                       N.sub.2 O       0.08 0.24      0.01                                           Na.sub.2 O      1.14 1.02      0.87 1.1                                       Al.sub.2 O.sub.3                                                                              1.0  1.0       1.00 1.0                                       SiO.sub.2       65.3 76.2      36.1 23.4                                      Catalytic Properties                                                          M-Forming Screening Test (600° F., 400 psig, 15 WHSV, 3/1 H.sub.2      /HC,                                                                          1.5 g. catalyst - charge 50/50 wt n-Heptane/Benzene)                          Type Catalyst   H.sup.+(2)     H.sup.+(2)                                     n-Heptane Conv., wt %                                                                         80.2           95.0                                           Benzene Conv., Wt %                                                                           32.0           27.8                                           C.sub.7.sup.+ Aromatics Prod., wt %                                                           28.9           27.4                                           Selectivity     0.32           0.28                                           __________________________________________________________________________     .sup.(1) These values are reduced to 0.03% for Example 8 and 0.05% for        Example 11. When uncalcined samples are exchanged with NH.sub.4 Cl.           .sup.(2) Calcination 1000° F. + NH.sub.4 .sup.+ Exchange          

We claim:
 1. In a method of synthesizing a crystalline aluminosilicateZSM-5 zeolite from a reaction mixture comprising water, sources ofsilicate, alumina and alkali metal, the improvement whereby the zeoliteis synthesized in a reaction mixture consisting essentially of saidsources and a member selected from the group consisting of (1) ZSM-5seeds, (2) mixtures of ZSM-5 seeds with alcohol, (3) mixtures of ZSM-5seeds with alcohol and ammonium hydroxide, and (4) mixtures of ZSM-5seeds with ammonium hydroxide to yield a zeolite ZSM-5 productcontaining no more than about 0.2% by weight of organic nitrogen.
 2. Themethod of claim 1 wherein said alcohol is an alkanol containing 2 to 5carbon atoms.
 3. The method of claim 2 wherein said alkanol is ethanol.4. The method of claim 1 wherein said member is ZSM-5 zeolite seeds. 5.The method of claim 4 wherein said seeds are from the residue of apreviously-prepared batch of ZSM-5 zeolite.
 6. The method of claim 1wherein said member is a mixture of alcohol and ZSM-5 zeolite seeds. 7.The method of claim 6 wherein the alcohol is ethanol.
 8. The method ofclaim 1 wherein said member is a mixture of ammonium hydroxide, ZSM-5zeolite seeds and an alkanol.
 9. The method of claim 8 wherein thealkanol is ethanol.
 10. The method of claim 1 wherein the seeds arepresent in an amount of from about 0.01 to about 10% by weight of finalproduct zeolite ZSM-5.
 11. The method of claim 1 wherein thealuminosilicate is synthesized in the presence of ZSM-5 seeds andammonium hydroxide.
 12. Process for preparing a synthetic crystallinezeolite molecular sieve having the chemical composition and X-ray powderdiffraction pattern of zeolite ZSM-5, which comprises forming an aqueousreaction mixture consisting essentially of inorganic reagents includingZSM-5 seeds and having the following compositions in terms of moleratios of oxides:SiO₂ /Al₂ O₃ :5-100 OH⁻ /SiO₂ :0.07-1.0 H₂ O/OH⁻:10-300 NH₄ OH/Al₂ O₃ :0-250and maintaining said reaction mixture at atemperature of from 75° C. to 175° C. for a period of six hours to 60days until crystals of the zeolite are formed.